EP0192008A1 - Detektor für dampfförmige Alkalimetalle - Google Patents

Detektor für dampfförmige Alkalimetalle Download PDF

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Publication number
EP0192008A1
EP0192008A1 EP85402598A EP85402598A EP0192008A1 EP 0192008 A1 EP0192008 A1 EP 0192008A1 EP 85402598 A EP85402598 A EP 85402598A EP 85402598 A EP85402598 A EP 85402598A EP 0192008 A1 EP0192008 A1 EP 0192008A1
Authority
EP
European Patent Office
Prior art keywords
gold
antimony
conductive element
detector according
detector
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP85402598A
Other languages
English (en)
French (fr)
Other versions
EP0192008B1 (de
Inventor
Jean-Claude Launay
Josik Portier
Bernard Tanguy
Francis Menil
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre National dEtudes Spatiales CNES
Original Assignee
Centre National dEtudes Spatiales CNES
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Centre National dEtudes Spatiales CNES filed Critical Centre National dEtudes Spatiales CNES
Priority to AT85402598T priority Critical patent/ATE49808T1/de
Publication of EP0192008A1 publication Critical patent/EP0192008A1/de
Application granted granted Critical
Publication of EP0192008B1 publication Critical patent/EP0192008B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid

Definitions

  • the invention relates to a vapor detector of an alkali metal, in particular sodium.
  • the molten alkali metals are placed in metal enclosures brought to temperatures which can exceed 1000 ° C., the vapor pressures then reach pressures of several bars. These enclosures are also subjected to thermal cycles. These technically severe conditions reveal constraints which can lead to damage to the heat pipe, (cracks, aging of the welds). Leaks can then appear which can cause alkaline fires which are particularly difficult to control. These fires constitute a danger for personnel. A very rigorous control of the alkali partial pressure must therefore be carried out in order to prevent such accidents.
  • the present invention proposes to provide an alkali metal vapor detector, in particular sodium, capable of fulfilling this mission.
  • the invention is based on the property that a gold wire or a layer of gold or antimony react quickly with the vapors of an alkali metal, especially sodium, with significant variation in its electrical conductivity. This variation in electrical conductivity can be used to generate a signal controlling the interruption of the electrical supply to the oven and the actuation of an alarm.
  • the invention relates to an alkali metal vapor detector, characterized in that it comprises a sensor comprising an electrically conductive element in gold or antimony, connected at its ends to two electrical conductors, means, connected to said conductors, for detecting a significant variation in the electrical resistance of the conductive element in gold or antimony, or of another electrical quantity dependent on said electrical resistance, resulting from the reaction of gold or antimony with vapors of an alkali metal, and a safety device controlled by said detection means.
  • the electrically conductive element can be a gold wire or a layer of gold or antimony deposited on a suitable support.
  • the invention applies mainly to the detection of sodium vapors but could also be used for the detection of potassium or other alkali metal vapors.
  • the invention will be described below more particularly with regard to the detection of sodium vapors.
  • the invention is based on the fact that a gold or antimony element reacts quickly with sodium vapors with significant variation in its electrical conductivity.
  • the increase in the resistance of the layer occurs around 230 ° C, temperature at which the partial pressure of sodium P Na is of the order of 0.13 Pa (10 -3 mm Hg).
  • a detector according to the invention based on gold therefore makes it possible to detect a partial sodium pressure of 0.13 Pa and more in the space of a few tens of seconds.
  • the increase occurs quickly and reaches its maximum in about 30 seconds.
  • the partial pressure of sodium PN is of the order of 42 Pa (3 X 10 -1 mmHg).
  • a detector according to the invention based on antimony therefore makes it possible to detect a partial sodium pressure of 42 Pa at approximately 360 ° C. in the space of a few tens of seconds.
  • the conductive element of the sensor can be a gold wire, for example a few tens of micrometers in diameter, or else a layer of gold or antimony deposited on an appropriate insulating support, by example of alumina.
  • the layer of gold or antimony can be produced by techniques known as a thick layer or a thin layer.
  • Thick layer conductive elements can be manufactured by screen printing of a composition based on gold on a suitable support, for example in alumina, drying and baking at high temperature intended to effect sintering.
  • Gold-based compositions useful for forming conductive patterns are well known in the field of printed circuits and commercially available from various manufacturers (in particular cios EI du Pont de Nemours and Company). These compositions generally include gold powder, a glass frit and a suitable diluent. Similar compositions based on antimony can be produced without difficulty. The layers thus produced have thicknesses in the range of 5 to 50 micrometers.
  • Thin film elements can be obtained by sputtering. It is well known that when a large potential difference is established between two electrodes immersed in an ionizable medium (rarefied gas), a projection of material from the cathode occurs.
  • an ionizable medium IR gas
  • the layers thus produced have thicknesses in the range of 0.01 to 1 micrometer.
  • a value of the layer resistance adapted to the measuring devices can be obtained by sandblasting the layer.
  • gold is meant both pure gold and alloys containing a major proportion of gold. It is the same for antimony.
  • the senor will be able to operate in different temperature ranges.
  • the gold layers obtained by the so-called thick layer technique are generally stable in the range from 20 to 700 ° C. approximately, being usually annealed around 850 ° C.
  • the gold layers obtained by cathode sputtering present a recrystallization phenomenon at 550 ° C which disturbs their electrical conductivity. They will therefore be used for applications in which they will be exposed to lower temperatures.
  • Gold threads will be useful for applications involving very high temperatures (above 700 ° C).
  • the layers of antimony they will be suitable for use in a temperature range from 250 to 500 ° C.
  • FIG. 2 is a block diagram of this detector.
  • the detector shown in FIG. 2 comprises a sensor 1 consisting of a thin layer of gold 2 of 0.1 ⁇ m thickness deposited on an alumina support and of two conductors 3, for example of copper tightened on the small opposite sides of layer 2 which has a rectangular shape (10 mm x 1 mm).
  • This sensor can be placed, for example, in an electric oven 4 with sodium heat pipes supplied with electric energy by a source 5.
  • the conductors 3 and the layer 2 are traversed by a current of constant low intensity I.
  • the resistance of layer 2 being equal to R (approximately 3 ohms initially), the voltage V across the terminals of layer 2 is equal to the product RI.
  • voltage V is compared in comparator 7 to a reference voltage Vref. If V is equal to Vref or is little different from it, no signal comes out of comparator 7.
  • the gold layer 2 reacts with sodium vapors, its resistance 5 increases sharply and the voltage across the terminals of layer 2 will also increase sharply, typically by a factor of 2, in the space of a few tens seconds.
  • the comparator 7 will then emit a signal which after shaping at 8 will activate the safety device 9. The latter will deactivate the source 5 of electrical energy and trigger the alarm 10, which can be, for example, audible and / or visual.
  • the device 9 could also control the activation of a specific fire extinguisher for alkali metal fires.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Biochemistry (AREA)
  • Electrochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
EP85402598A 1985-01-07 1985-12-23 Detektor für dampfförmige Alkalimetalle Expired - Lifetime EP0192008B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85402598T ATE49808T1 (de) 1985-01-07 1985-12-23 Detektor fuer dampffoermige alkalimetalle.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8500127A FR2575832B1 (fr) 1985-01-07 1985-01-07 Detecteur de vapeurs d'un metal alcalin
FR8500127 1985-01-07

Publications (2)

Publication Number Publication Date
EP0192008A1 true EP0192008A1 (de) 1986-08-27
EP0192008B1 EP0192008B1 (de) 1990-01-24

Family

ID=9315039

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85402598A Expired - Lifetime EP0192008B1 (de) 1985-01-07 1985-12-23 Detektor für dampfförmige Alkalimetalle

Country Status (4)

Country Link
EP (1) EP0192008B1 (de)
AT (1) ATE49808T1 (de)
DE (1) DE3575606D1 (de)
FR (1) FR2575832B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT404995B (de) * 1996-11-07 1999-04-26 Ica Innoconsult Ag Verfahren zum dosieren von korrosionsschutzmitteln

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2202596A5 (de) * 1972-10-06 1974-05-03 Westinghouse Electric Corp
US3950980A (en) * 1974-03-27 1976-04-20 Minnesota Mining And Manufacturing Company Vapor sampling device
FR2316597A1 (fr) * 1975-07-02 1977-01-28 Westinghouse Electric Corp Methode et appareil pour la detection extremement sensible de vapeur metallique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2202596A5 (de) * 1972-10-06 1974-05-03 Westinghouse Electric Corp
US3950980A (en) * 1974-03-27 1976-04-20 Minnesota Mining And Manufacturing Company Vapor sampling device
FR2316597A1 (fr) * 1975-07-02 1977-01-28 Westinghouse Electric Corp Methode et appareil pour la detection extremement sensible de vapeur metallique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT404995B (de) * 1996-11-07 1999-04-26 Ica Innoconsult Ag Verfahren zum dosieren von korrosionsschutzmitteln

Also Published As

Publication number Publication date
FR2575832A1 (fr) 1986-07-11
EP0192008B1 (de) 1990-01-24
ATE49808T1 (de) 1990-02-15
DE3575606D1 (de) 1990-03-01
FR2575832B1 (fr) 1987-03-27

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